Coating machine



v May 6, 1941- H. w. WEINHART 2,241,228

COAT ING MACHINE Filed March 3, 19259y 3 Sheets-Sheet l /NVE/VTOR H. W. WE/NHART 2 A7' TORNEV May 6 1941- H. wf wElNHART 2,241,228

coATING MACHINE Filed March 3, 1939 3 Sheets-Sheet 3 111/ lll/1 11111/ 1 /NVENTOR hi W WE /NHART A77' ORNE y Patented May s, 1941 UNITED STATES PATENT OFFICE amm COATING MACHINE Howard W. Wcinhart, Elizabeth, N. J., assignor to Bell Telephone laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 3, 1939, Serial N0. 259,623

9 Claims.

'I'his invention relates to a coating machine and particularly toa machine for applying metallic coatings to objects by the thermal evaporation process.

An object of the invention is to facilitate the application of metallic coatings to objects.

A more speclc object of the invention is to facilitate and render more economical the application of metallic electrode coatings to piezoelectric crystal plates.

Piezoelectric crystal plates are, as is well known, commonly used as elements in electrical circuits where a. constant frequency is essential and are of increasing importance as elements of electrical lters and other networks. When these plates are used in electrical circuits it is necessary, of course, that some means be provided whereby the plates may be electrically connected to the other elements of the circuit. It is common practice to provide for this purpose metallic electrode coatings, such, for example, as a thin nlm of aluminum on the surfaces of the crystal plate, these coatings being electrically conductive with respect to the surface to which they are applied. The external conductors of the circuit may then be connected to the proper electrode coatings'by suitable means.

The machine of the present invention is particularly adaptable to the application of such coatings to the surfacescf piezoelectric crystal plates. l

In accordance with a specific embodiment ot the' invention, a plurality of evaporation chambers are provided, all of which may be exhausted by a common evacuating means. Each chamber is provided with'suitable heating elements for bringing about evaporation of the coating ma,- terial.

A feature of the inwntlon is separate high pressure and low pressure exhausting paths for each chamber.

Another feature of the invention is means whereby the high pressure and the low pressure path of each chamber may be operated entirely independently of each other.

A further feature of the invention is means whereby the pressure within any one of the chambers may be raised or lowered without materially affecting the pressure within the other chambers. v

A still further feature of the invention is a readily removable unit for each chamber, which unit includes a table for supporting the plates to be coated and the heater filament assembly.

A complete understanding oi the arrangement and functioning of the machine contemplated by the present invention as well as appreciation of the various valuable features thereof may be gained from consideration of the subsequent detailed description in connection with the drawings in which:

Fig. 1 is a perspective view of a coating ma`- chine embodying features of the present invention;

Fig. 2 is an end view of the machine shown in Fig. 1:

Fig. 3 is a sectional view of one of the evaporation chambers;

Fig. 4 is a perspective view of one of the remov able table supporting units;

Fig. 5 is a, view of a portion of one of the filaments;

l Fig. 6 is a sectional view taken on line 6-8 of Fig. 3`showing the details of the air intake valve;

Fig. 7 is a sectional view taken on line 1--1 of Fig. 3 showing details of the unit within the evaporation chamber; and

Fig. 8 is a sectional view taken on line 8-8 of Fig. 7 showing details of the terminal member and connector spring.

Referring now to the drawings, there is shown in Fig. 1 a coating machine assembly mounted on a suitable base member 2|. The assembly illustrated includes six evaporation chambers 22, 23, 24, 25, 26 and 21 and three tubes 3|, 32, and 33. Manifold tube 3l (Fig. 2) is connected through pipe 34 directly to unit 35 of an oil diffusion vacuum pump while manifold tube 33 is connected through pipe 36 directly to mechanical oil vacuum pump 3l. Pump 31 is driven by motor 5i. Unit 52 of the oil diffusion pump assembly -is connected in series with unit 35 thereof through pipe 53 (Fig. 1), gas storage reservoir tube 32 being connected through pipe 64 (Fig. 2) directly to unit 52 (Fig. 1) of the diffusion pump.

A resilient portion 55 is provided in pipe 38 in order to prevent the transmission of undesirable vibrations from mechanical pump 31 to the evaporation chambers.

Manifold tube 3| and storage tube 32 which are connected to the oil diffusion vacuum pump (through pipes 3l and 54, respectively) comprise what may be called the low-pressure section of the pumping system while manifold tube 33, which is connected to mechanical oil vacuum pump 31 through pipe 36, comprises what may be called the high-pressure section of the system.

Each of the evaporation chambers is connected directly to manifold tube 33 by means of a short pipe connected at the rear of each chamber. For

` ber.

example, pipe 56 connects chamber 22 to manifold tube 33, pipe 51 connects chamber 23 thereto and so on. Each of these six connecting pipes is provided with a shut-ofi valve. For example, pipe 56 is provided with shut-ofi valve 6|, pipe 51 with shut-ofi valve 62 and so on.

Each of the evaporation chambers is also. connected directly to manifold tube 3| through a short pipe located near the iront of each cham-l For example, chamber 22' is connected to manifold tube 3| through pipe 63, chamber 23 through pipe 64 and soon. Each of these short l connecting pipes is provided with two valves, one4 and air intake valve 66v while connecting pipe 64 is provided with shut-off valve 61 and air intake valve 68. Each of the air intake valves controis the admission o! ai; through an aperture from the outside atmosphere.y For example, as shown in Fig. 6, valve 66 controls the admission of air through aperture 68.

Shut-oil valve 82 is provided for ee'ctively separating upon occasion the high pressure section from the low pressure section of the pumping-system.

Each of the evaporation chambers is provided with a closure capfior example, chamber 22 is closed by cap 6|, chamber 23 by cap 62 4and so on. Each of these caps is provided with a handle,as 83 and 84, for convenient manipulation. Each .cap removably supports a -unit including a table for supporting the plates to be coated and the heater filament assembly. By way' of example, the u nit provided in chamber 22 will now be described.

As clearly shown in Figs. 3 and 4, a plate 85 is mounted on the inner 96 and 81, of Iconductive material are rigidly supported by plate 66, Vbeing electrically insulated therefrom by suitable bushings and washers of insulating material, bushing 98 and washer 86 being shown. A metal table is supported by rods-96 and 81 being electrically insulated therefrom by suitable mounting blocks of insulating material, block being shown in Fig. 3. This table serves as a support for the plates being coated. A number of plates; as, ||2 and H3, are shown (Figi.) in position on table III. Terminal posts III and ||5 are provided at one end of of cap 8|. Two rods,

,be coated and that tact i26 by bolt |3| (Fig. 8); terminal member t28 is similarly connected to a like contact spring, (not shown). When the unit is in position within the chamber, bar 91 is electrically connected to terminal member |21 by spring |26 and bolt |3| bar 86 is electrically connected to terminal member |26 in a similar manner. This connecting means provides a convenient arrange- I ment for connection between the removable unit and the external circuit elements.

The necessary switches, rheostats, meters and other apparatus incidental to the control of the electrical current are mounted in control box |6| The electrical current .is supplied 'to the leadin terminals |21, |28, |52, |53, and so on, of the evaporation chambers through suitable exible conductors, not shown.

The chambers of the oil diii'usion vacuum pump and each evaporation chamber 'are surrounded by coils of tubing.; this tubing terminates in sections |54 and |55 to which may be connected the terminals of a suitable pumping system, not shown-for. the supply of a cooling fluid which may be water.

lIn order to further illustrate the invention, the actual operation ci the machine contemplated thereby will now'be described. Let us assume that all oi' the evaporation chambers, 22 to 21, have been loaded withpiezoelectric plates to l all the closure covers, as 9|, are' in position.

All air-intake valves, as 66 and 68, are closed,

` thereby preventing entry of air from the surare opened, thereby connecting the chambers to rods 66 and 81; terminal posts H6 and ||1l are' mounted on plate 95.- Terminals ill and ||5 are electrically Vdistinct while terminal posts H6 suspended on each iilament wire being pinched tightly to the lament to prevent shifting.

The filament wires are maintained under a substantially constant tension due to the resilient mountings provided for terminals lil and H5, each of which mounting is provided with a tensioning spring, such as spring |20 (Fig. 3).

Bushing lugs v|24 and |25 are mounted on chamber 22 (F18. 7) and support terminal members. |26 and |21, respectively. Terminal member |21 is electrically 4connected'to spring conthe .high-pressure side ofth'e system. Valve 62 is closed, thereby separating the two systems from each other.

Mechanical oil pump 31 is n ow 'set into operation and as much of the'air as possible is removed trom the chambers through the highpressure side of the pumping system, pump 31, as pointed out above, being co'nnected, directly to high-pressure manifold tube 33. The airis discharged through a ventlprovided on the output side of pump 31. l

After as much of the air as possible hasbeenremoved by use of the mechanical oil pump, valves 6|, 62, and so on, are closed, valves 65, 61, and so on, and valve 62 are opened and the oil diiIusion vacuum pump is s'et into operation to remove more of the air through the low-pressure side of 'the system (manifold tube 3| and storage reservoir 32), the air being discharged through manifold tube 33, pipe 36 and the vent on the output side of mechanical pump 31. The preliminary removal of a large part of the air by means of the mechanical pump prevents an undesirable rush of air through the low-pressure system; provision of the oil diffusion pump permits achievement of a lower pressure than' could be obtained by means 0i the mechanical pump alone.

When a sumciently low pressure hasbeen attained in the chambers, the electrical current is turned on and the illaments are heated to a temperature that causes the aluminum hair-pins supported on lthe illaments to evaporate; the evaporated material condenses on'the surfaces of the crystal plates forming the desired metallic coating thereon.

The electrical heating circuit referred to above lay be traced, with reference to chamber 22 Figs. 8. 4, 'I and 8) as follows: terminal' |21, ol-NII, spring |26, rod Il, terminal I I5, filament 22, terminal H1, conductive strip I2I, terminal II, filament |22, terminal III. rod li,` and hrough a spring and bolt (not shown but simlar, respectively. to spring |28 and bolt lli) to erminal member |28. The circuits of the other erminals are completed in a similar manner.

Let us assume now that we wish to open evaporation chamber 22 in order to remove the )lates therefrom, without affecting the pressure n the other evaporation chambers. Valve il is irst closed, thereby'shutting off chamber'22 from he low-pressure side of the pumping system. Valve it is then opened in order to admit air nto chamber 22 so that the chamber may be ipened. Cover il may now be removed by use )f handle I3 and the unit supported thereby withdrawn from the chamber.

After the unit has beenreplaced in chamber 22 and cover I i closed, valve 6C is again closed. Valve l2 is closed and valve 8| is opened whereupon most of the air in chamber 22 is removed by mechanical pump 31 through pipe II, manifold 3l and pipe I0. During this time, i. e., while valve 82 is closed, any air collected in the low pressure side of the system will be temporarily stored in gas storage reservoir tube l2. After as much of the air as possible has been removed by pump I1, valve Mis closed and valves 02 and i are opened, thereby again connecting the chamber to the low pressure side of the system. In view of the fact that most of the air has already been removed from chamber 22, the pressure of the other chambers is not materially changed when chamber 22 is reconnected to the low pressure side. In like manner, of course, any of the other chambers may be opened without affecting the pressure in the other chambers.

'While a specific embodiment of the invention has been selected for detailed description, the invention is not, of course, limited in its application to the embodiment disclosed. 'I'he embodiment described should be taken as illustrative of the invention and not as restrictive thereof.

What is claimed is:

l. Apparatus for coating a surface of an object by thermal evaporation comprising a plurality of evaporation chambers adapted to receive the objects to be coated, a filament in each of said chambers, means for heating said laments, common means for exhausting the air from all of said chambers, means for changing the air pressure in any of the chambers and means for maintaining the pressure in the other 'chambers unvaried irrespective of the operation of said pressure changing means.

2. Apparatus for coating a surface of an obf ject by thermal evaporation comprising a plurality of evaporation lchambers adapted to receive the objects to be coated, a filament in each of said chambers, means for heating said filaments. a manifold, pressure in said manifold, means for individually connecting each of said chambers to said manifold, means for effectively 'disconnecting each of said chambers from said manifold, and means for controlling admission of the free atmosphere to each of said chambers.

3. Apparatus for coating a surface of an object by thermal evaporation comprising a plurality of evaporation chambers adapted to receive the objects to be coated, a filament in each of said chambers, means for heating said filaments, a manifold, means for producing a low pressure in said manifold, pipes for individually connecting each of said chambers to said manifold, a valve in each of said pipes for effectively disconnecting each of said chambers from said manifold, and a second valve in each of said pipes for controlling admission of the free atmosphere .to each of said chambers.

4. Apparatus for coating a surface of an object by thermal evaporation comprising a plurality of evaporation chambers adapted to receive the objects to be coated, a filament in each of said chambers, means for heating said filaments, a manifold, means for producing a low pressure in said manifold, pipes for individually connecting each ofV said chambers to said manifolds each of said pipes having an aperture .therein for admission of the free latmosphere to said chambers, a valve in each of said pipes for closing said apertures. and a second valve in each of said pipes for effectively disconnecting the associated chamber from said manifold whereby admission of air to one of said chambers through one of said apertures does not affect the pressure in said manifold.

5. Apparatus for coating a surface of an object by thermal evaporation comprising a plurality of evaporation chambers adapted to receive the objects to -be coated, a filament in each of said chambers, means for heating said filaments, a manifold, means for producing a low pressure in said manifold, pipes for individually connecting each of said chambers Ito said manifold, a valve in each of said pipes for effectively disconnecting each of said chambers from said manifold, a gas storage tube, means for connecting said manifold through said low pressure producing means to said storage tube, a second manifold, means for producing a low pressure in said second manifold, pipes for individually connecting each of said chambers to said second manifold, a valve in each of said last-mentioned pipes for effectively disconnecting each of said chambers from said second manifold, a pipe for connecting said second manifold and said gas storage tube, and a valve in said last-mentioned means for producing a low pipe for effectively disconnecting said gas storage tube from said second manifold.

, 6. Apparatus for coating a surface of an object by thermal evaporation comprising a cylindrical open-ended evaporation chamber, removable means for closing the open end of said chamber, a filament adapted to be positioned within said chamber, means for supporting said filament from said closing means, an electrical terminal mounted on ,the outside of said chamber, and means mounted within said chamber effective to electrically connect said terminal and said filament when said closing means is in position rto close-said chamber.

7. Apparatus for coating a surface of an object bythermal evaporation comprising a cylindrical open-ended evaporation chamber, removable means for closing the open end of said chamber, a filament adapted to be positioned within said chamber, means for supporting said filament from said closing means, a conductor member supported by said closing means, means for electrically connecting said filament and said conductor member, an electrical terminal mounted on the outside of said chamber. and an electrically conductive spring member-electrically connected to said terminal and mounted within said chamber in a position to. engage said conductor member when said closing means is in position "to close said chamber, thereby electrically connecting said filament to said terminal.

8. Apparatus for `coating a surface of an object by thermal evaporation comprising a plurality of cylindrical, open-ended evaporation chambers, a cap for each chamber adapted to close the open end thereof, a plurality of rigid electrical conductor members carried by said cap, a. table carried by said conductors adapted to support the objects to be coated, a plurality of'iilaments can-im by said cap and supported above said table, means for conductively connecting each of 2,241,928 within the chambers that contact is made by each spring member with one of said rigid conductors when said cap is in position to close the `associated chamber.

9. Apparatus for coating a surface oi' an object by -thermal evaporation comprising a plurality of evaporation chambers adapted to receive the objects to be coated, a filament in each of said chambers, means for heating said filaments, a manifold connected to Said chambers, means for exhausting air from said chambers through said manifold, means associated with each of said chambers for controlling the admission of air thereto from the surrounding atmosphere, means for preventing the entry oi such admitted air .to said manifold, and means independent of said manifold for exhausting such admitted air from any of said chambers without entry of such air into said manifold.

HOWARD iifEiNHART- 

